Bike Size Calculator

How to use the calculator

1. Pick your type of bike. Each type has its own chart: a medium mountain bike does not measure the same as a medium road bike.
2. Enter your height barefoot. That alone gives you your size.
3. Add your inseam if you know it (open How to measure your inseam). It tells us whether your legs are long or short for your height, which is what decides when you are between two sizes, and it gives you your saddle height.
4. Check the chart for the type you picked. Your size is highlighted.

Save to My Bike stores your height and inseam for the other calculators, like the saddle height and crank length calculators.

How to measure your inseam

Your cycling inseam is not your pants inseam: it is longer, because you measure all the way up to the bone, pressing the way a saddle does.

1. Stand barefoot with your back against a wall and your feet about 6 in (15 cm) apart.
2. Put a hardcover book between your legs, spine up, and pull it up firmly.
3. Keeping the book level, mark the top edge on the wall.
4. Measure from the floor to the mark. Repeat and take the average.

Your inseam is normally 44% to 48% of your height. If you get much less, you probably did not press the book up hard enough.

How we calculate your size

By height. We compared the published size charts from Canyon, Giant, Orbea, Trek and Specialized for each type of bike and built a generic chart from the consensus, rounded. Your size is the row your height falls in.

Between two sizes. If you are within 0.6 in (1.5 cm) of the boundary, we flag it. Then we look at the ratio between your inseam and your height:

Ratio = inseam ÷ height

• Above 0.475 (long legs, short torso): go smaller. You will reach the bars without stretching and run more seatpost.
• Below 0.445 (short legs, long torso): go bigger, which gives you more reach (the horizontal distance from the bottom bracket to the handlebar).
• In between: either one works, and your flexibility and riding style decide. The smaller size has less stack (lower bars) and less reach (bars closer); the bigger one, more reach. With limited flexibility, back pain or long easy rides, the smaller frame with a spacer or two under the stem usually fits better; with good flexibility or if you want a race position, the bigger one. On a mountain bike, the smaller size is nimbler on slow trails and the bigger one more stable descending.

By inseam (the old-school method). We also give you the traditional size: inseam × 0.665 for road bikes (seat tube length in cm, center to top) and × 0.226 for mountain bikes (in inches, using your inseam in cm). It is a general rule of thumb, not any brand’s, and it fits modern bikes less well because frames now have sloping top tubes and shorter seat tubes. Treat it as a secondary number.

Saddle. With your inseam we work out your saddle height as the average of the LeMond and 109% methods. The saddle height calculator lets you fine-tune it with your crank length and cleats.

Bike size chart by height

Our generic charts, XS to XL, with the usual frame size after the height range (on mountain bikes, seat tube length in inches):

And the same charts read the other way, by your height:

E-bikes use the same ranges as regular bikes in their family: an e-MTB, the mountain chart; an electric hybrid or commuter, the hybrid chart. On gravel bikes the small sizes start a little earlier (XS from 5 ft 1 in / 155 cm, S from 5 ft 4 in / 162 cm), and mountain bikes are where brands differ most: Trek and Specialized start each size 2-4 in (5-10 cm) lower than Canyon.

The full charts, from 4 ft 11 in to 6 ft 7 in (150-200 cm) and with XXS, XXL and triathlon, are in the bike size chart by height; with inseam, in the road and mountain charts, and brand by brand in sizes by brand.

Why every brand sizes differently

• Letter sizes are not standardized. Canyon labels one letter lower than everyone else: its small road bike (5 ft 8 in to 5 ft 10 in, 172-178 cm) matches a Giant or Specialized medium.
• Geometry matters more than the letter. Two medium bikes can differ by 20 mm in stack (the height from the bottom bracket to the top of the head tube) and in reach. A race bike is lower and longer than an endurance bike of the same size.
• Ranges overlap. Giant and Trek give ranges that overlap by 1-4 in (3-10 cm) between sizes: at 5 ft 10 in (178 cm) you can ride two different sizes of the same bike.

That is why this calculator gives you a starting size. Before you buy, check the chart for the exact model (the best-selling brands are in sizes by brand) and, if you can, test ride it.

Common mistakes

• Measuring your height in shoes. That adds about 1 in (2-3 cm) and can bump you up a size.
• Going by the size of your last bike if it is a different brand or type.
• Buying big “so it lasts.” For adults, a bike that is too big makes you stretch, loads your back and cannot be fixed with a stem.
• Fixing the wrong size with a 60 or 140 mm stem. It changes how the bike steers. Road bikes normally run stems of 80 to 110 mm.
• Forgetting the saddle. A perfect size with the saddle in the wrong place is still uncomfortable.

How to check the size at the bike shop

• Standing over the bike with your feet flat, there should be some clearance between your crotch and the top tube.
• Seated, with your hands on the hoods, your elbows should be slightly bent and your back relaxed.
• With the saddle at your height, the seatpost has to sit above its minimum insertion mark and not past the maximum.

Shopping for a kid? Use the kids’ bike size calculator or check size by age.

Updated October 19, 2026 ·Report an error on this page